Interpretive Summary: Evaluation of potential repellent compounds against mosquito vectors of diseases is time consuming and often involves animal or human subjects. We have developed a laboratory modular assay system that can screen candidate compounds without involving human subjects or animals. This assay system is compact in size and only requires small amounts of the test compound. These findings support previous laboratory and field studies showing man-vector contact and disease transmission are routinely interrupted by spatial repellent and contact irritant actions of common public health insecticides. This information can be used by scientists in the private and public sectors that are interested in developing and testing potential repellent compounds.

Technical Abstract:
A previously described modular high-throughput screening system (HITTS) was used to characterize the spatial repellent, contact irritant and toxicant chemical actions of 14 compounds with a history of use in vector control. The response of F1-F4 Aedes aegypti to various concentrations of four organochlorines (chlordane, DDT, dieldrin, methoxychlor); four pyrethroids (alphacypermethrin, cypermethrin, deltamethrin, permethrin); three organophosphates (chlorpyrophos methyl, fenitrothion, malathion); two carbamates (bendiocarb, propoxur); and one Pyrazole (chlorfenapyr) were evaluated. Results show chemicals exert different combinations of contact irritant, spatial repellent and toxic actions. This is true even within the same chemical class. These actions can be ordered for each chemical based on the testing dose at which the specific response is elicited. Data also indicate that behavioral responses to spatial repellent and contact irritant actions are separate (or independent) from the toxic action of a compound. Results from pyrethroid and DDT(or Organochlorines?) assays also show chemicals can induce behavior-modifying actions, such as contact irritancy and spatial repellency, which will reduce man-vector contact, despite evidence of insecticide resistance within the test population. This study supports previous observations that impact of public health insecticides on vector populations is much more complex than just toxicity.